Physical and compact modeling of resist deformation (Conference Presentation)

Abstract

Chemically amplified resists undergo various chemical phenomena during the photolithography process such as exposure, post-exposure bake (PEB), and development. These chemical changes induce various stresses causing the deformation of exposed region of photoresist. It is imperative to include these deformations in the modeling of lithographic processes especially for negative tone development (NTD) process, where an exposed and deformed part of the resist stays on the substrate after development. We use rigorous physical model to express the stresses induced by voids created in resist by evaporation of the protecting species. Finite Element method (FEM) is then used to solve three-dimensional elastic deformation equations for resist during PEB and development. The deformation of resist is studied for both one-dimensional gratings and two-dimensional contact holes with varying pitch and optical doses, and we discuss how different modes of deformation are important to be considered in the lithography simulations in order to reduce the critical dimensions’ (CD) computation error. Finally, we briefly introduce a compact model where Fourier series are used to find the exact analytical solution of elastic deformation equations. The results of compact model are compared with the rigorous FEM solution. The compact model is suitable for full chip lithography simulations due to it being numerically fast operations and results comparable to full-physics rigorous simulations.